Silica (SiO2) films formed by vacuum processes such as the CVD method have hitherto been used frequently as dielectric films in semiconductor devices and other devices. In recent years, a dielectric film which comprises a tetraalkoxysilane hydrolyzate as the main component and is called an SOG (spin on glass) film has come to be used for the purpose of forming a more even dielectric film. Furthermore, as a result of the trend toward higher degree of integration in semiconductor devices and the like, a dielectric film called an organic SOG film has been developed which comprises a polyorganosiloxane as the main component and has a low dielectric constant.
However, with further progress in the high integration or multilayer film interconnection in semiconductor devices and the like, better electrical insulation between metal lines and vias has come to be required and, hence, a dielectric film has come to be desired which has satisfactory storage stability, a lower dielectric constant, and excellent leakage current characteristics.
JP-A-6-181201 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a dielectric film having a lower dielectric constant. This technique is intended to provide an insulating film for semiconductor devices which has low water absorption and excellent cracking resistance. This insulating film is formed from a composition which comprises as the main component an oligomer having a number average molecular weight of 500 orhigher obtained by condensation-polymerizing an organometallic compound containing at least one element selected from titanium, zirconium, niobium, and tantalum with an organosilicon compound having at least one alkoxyl group in the molecule.
JP-A-10-237307 and WO 97/00535 disclose techniques for curing an SOG film with electron beams, which comprise irradiating a resin comprising a siloxane resin as the main component with electron beams. These techniques are intended to convert a siloxane resin into silica (SiO2) by electron beam irradiation. The insulating film thus obtained usually has a dielectric constant of from 3.5 to 4.2, which is still too high to apply the insulating film to semiconductor devices which operate at a high frequency.